The present invention relates to a method and apparatus for regulating an increase in an engine speed at the time of first combustion during start-up, and to a personal watercraft equipped with the apparatus.
There are various kinds of engines used as a drive source of vehicles and among those engines, there is a multi-cylinder engine which is configured to adjust an amount of intake air of the whole engine by a single throttle valve. In this multi-cylinder engine equipped with such a single throttle valve, in order to realize a stabilized operation even in a low rotational speed range without being influenced by intake-air pulsations between cylinders, compared with an engine having multi-throttle valves, it is necessary to consider a setup which opens the throttle valves more greatly. As a result, significant engine noise not only occurs, but the engine speed may increase rapidly at the time of first combustion during start-up and, thus, vibrations of the engine may increase.
In personal watercraft (PWC) which are equipped with a water jet pump, since an output shaft (i.e., a crankshaft) of the engine is directly connected with an input shaft (i.e., a pump shaft) of the water jet pump substantially without engaging a component such as a clutch, when an engine speed is increased, thrust of the watercraft is generated by the water jet pump and then the watercraft may unintentionally move at start-up.